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Summary Plants of Phaseolus vulgaris were grown for a period of 4 weeks in nutrient solutions deficient in S, Mg, K, N, P and Fe, and compared with controls growing in complete nutrient solutions. At weekly intervals, tissue from all leaf groups fully expanded at the time of sampling was prepared for examination under the electron microscope. It was possible to examine chloroplast ultrastructure, firstly, during leaf development under each of the nutrient deficient conditions and, secondly, to compare the chloroplasts of similar leaf groups produced under different deficiency conditions. Although distinctive chloroplast types could be associated with conditions of Mg, K, N and Fe deficiency, chloroplasts from S and P deficient plants were variable in appearance. The chloroplast patterns produced were found to be consistent in palisade parenchyma tissue but in spongy mesophyll tissue cells frequently appeared plasmolysed and chloroplasts varied considerably in appearance. Particularly in the spongy mesophyll distinctive crystalline configurations were found within the chloroplasts.

Summary Parenchyma cells in the leaf sheath of Equisetum telmateia form linearly arranged series of maturing and senescing cells. These series of cells contain chloroplasts showing a progressive sequence of developmental stages easily recognizable because of the spatial relationships involved. The cell sequence may be classified into four successive zones, characterized by the typical structure of the chloroplasts present in the cells of each zone. Zone I. Meristematic cells contain immature chloroplasts with little internal lamellar structure. Zone II. Adjacent to the above are cells containing mature chloroplasts with a well-developed internal lamellar system. Zone III. Next in sequence are cells in which the chloroplasts retain a mature internal lamellar system but are distinguished from the previous group by the presence of irregular osmiophilic deposits around the outer double membranes. Zone IV. Finally there occur cells with usually rounded chloroplasts which show the osmiophilic deposits described above, but in which the outer double membrane is often difficult to distinguish. Internally the lamellar system is highly sinuous, and contains many swollen locules. In spite of a general similarity in appearance between chloroplasts of Equisetum and those of angiosperms, Equisetum plastids are characterized by a distinctive feature more commonly associated with algae than with higher plants. Young chloroplasts are almost completely surrounded by rough endoplasmic reticulum. This very close relationship between reticulum and chloroplast is retained as the chloroplast matures, though the degree of envelopment becomes less with increasing age.

Summary The ultrastructure of mature guard cells of Phaseolus vulgaris L. grown under continuous light regime showed remarkable stability, remaining constant in appearance under a wide range of conditions of nutrient deficiency. The ultrastructure was quite unlike that of leaf parenchyma cells of normal plants, but had certain characteristics similar to those found in palisade parenchyma cells suffering from magnesium and potassium deficiency.